RFC 2328: OSPF Version 2 defines OSPF network types. In this article, we are going to discuss the two major network types, which are Point-to-Point and Broadcast. As a network engineer working with OSPF, you must understand the differences between each OSPF network type and their compatibility. Some types will function together, but the hello and dead timers must be adjusted. The following list indicates which OSPF network types can communicate with one another: Show
A Point-to-Point network type is, as its name implies, a connection between two specific points (or OSPF routers). On a point-to-point link, a packet delivered from one of the routers will always have precisely one recipient. It does not maintain a DR/BDR relationship, and it has a 10-second hello and 40-second dead timer. Leased lines running Point-to-Point Protocol (PPP) and High-Level Data Link Control (HDLC) are some examples of point-to-point links. BroadcastThe broadcast network type is the default network type for an OSPF-enabled Ethernet interface. It requires a link that supports Layer 2 broadcast. It requires the use of a DR/BDR relationship, and it has a 10-second hello and 40-second dead timer. Configuring the Network TypesOSPF is a very versatile protocol. Take into account its capacity to support both broadcast and non-broadcast multi-access (NBMA) network types. OSPF responds by changing its operation to match the settings you’ve provided. OSPF makes an attempt to detect physical media and defaults to the appropriate behavior. If you don’t like the default behavior, you can override it using the following command: Router#conf t Router(config)#int gi0/0 Router(config-if)#ip ospf ne Router(config-if)#ip ospf network ? broadcast Specify OSPF broadcast multi-access network non-broadcast Specify OSPF NBMA network point-to-multipoint Specify OSPF point-to-multipoint network point-to-point Specify OSPF point-to-point network Let’s have an example. We can see below that the default network type is Broadcast and with DR neighbor. Router#sh ip ospf int gi0/0 GigabitEthernet0/0 is up, line protocol is up Internet Address 10.1.1.1/30, Area 0, Attached via Network Statement Process ID 1, Router ID 1.1.1.1, Network Type BROADCAST, Cost: 1 Router#sh ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 2.2.2.2 1 FULL/DR 00:00:34 10.1.1.2 GigabitEthernet0/0 Change the interface network type from Broadcast to Point-to-Point: Router#conf t Router(config)#int gi0/0 Router(config-if)#ip ospf network point-to-point Upon checking again, we can see that the network type is now POINT_TO_POINT. Router#sh ip ospf int gi0/0 GigabitEthernet0/0 is up, line protocol is up Internet Address 10.1.1.1/30, Area 0, Attached via Network Statement Process ID 1, Router ID 1.1.1.1, Network Type POINT_TO_POINT, Cost: 1 If we check the OSPF neighbor again, we will no longer see the DR/BDR relationship. Router#sh ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 2.2.2.2 0 FULL/ - 00:00:37 10.1.1.2 GigabitEthernet0/0 Why would not having a DR/BDR neighbor be beneficial? Assume you have a point-to-point network. Because there is only one
other router to communicate with, you can reduce router memory and CPU consumption by not using neighbors. In this instance, having a basic adjacency works nicely. Download our Free CCNA Study Guide PDF for complete notes on all the CCNA 200-301 exam topics in one book. We recommend the Cisco CCNA Gold Bootcamp as your main CCNA training course. It’s the highest rated Cisco course online with an average rating of 4.8 from over 30,000 public reviews and is the gold standard in CCNA training: An OSPF interface includes the following timers:
To set OSPF timers:
What is the default OSPF hello and dead interval on non broadcast multi access network?OSPF Hello Interval and Dead Interval
The defaults are 10 seconds for an Ethernet link and 30 seconds for a non broadcast link.
What is the default value for the OSPF dead interval?Dead interval in seconds. Valid values range from 3 through 65535 seconds. The default is 40.
What are the default values for hello and dead packets in OSPF?The default values are 10 seconds for the hello time, and 40 seconds for the dead time. The usual rule of thumb with OSPF is to keep the dead time value four times the hello interval.
What is OSPF Hello timer and dead timer?Hello timer—Interval for sending hello packets. It must be identical on OSPF neighbors. Poll timer—Interval for sending hello packets to a neighbor that is down on the NBMA network. Dead timer—Interval within which if the interface does not receive any hello packet from the neighbor, it declares the neighbor is down.
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What is the default OSPF hello and dead interval on non broadcast multiaccess network?
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